On the impact of salinity observations on state estimates in Ems Estuary

The hydrodynamics of Ems Estuary are dominated by tides and their interaction with buoyancy forcing. Such an environment is challenging for any effort to bring together observations and model results. In this study, we investigate how salinity measurements in the Ems Estuary affect the reconstruction of the salinity field. Similar to the traditional observing system experiments, the impact of specific observational arrays is simulated in the framework of statistical experiments. The experimental algorithm mainly relies on the model covariance matrix. Each experiment results in an estimate of the reconstruction error. The analysed observation configurations involve single and multiple, as well as stationary and non-stationary observing arrays. Generally, the reconstruction of the ocean state improves with increasing the density of observations. It appears that certain locations are more favourable for reconstruction than others. In fact, the regions separating the main dynamical realms resist strongest to the reconstruction effort. Extending the covariance matrix by the temporal cross-covariances between the model grid points enables to evaluate the impact of observations taken from a moving platform. This approach further improves the outcome of the experiments, resulting in reconstruction errors near zero with the exception of the tidal river. The cross-covariance information is able to tackle even the irregular dynamics arising on the border between the different physical regimes.     

The Influence of a Local Fault Zone on High Energy Tremor Occurrence During Longwall Mining of a Coal Seam

Underground mining of coal seams in the Upper Silesian Coal Basin in Poland is accompanied by seismic activity of varying magnitude. The investigations which have been performed for several years distinguished high energy mine tremors connected directly with mining or coupled with geological structures, such as large faults. In mined seams, local fault zones occur. Faults in these zones are usually small, with throws comparable with coal seams thicknesses. Local fault zone may be responsible for the occurrence of high energy tremors as well as large faults, as presented in this article. An analysis of source mechanism of high energy tremors generated during longwall mining of the coal seam No. 510, with presence of a local fault zone, in one of the Polish hard coal mines in the Upper Silesian Coal Basin was performed. For this purpose, the seismic moment tensor inversion method was used. In most of foci, the process of shear predominated. Determined nodal plane parameters were correlated with parameters of faults forming the local fault zone. High energy tremors were generated mostly by dislocations on faults of the local fault zone. Weakening of roof rocks in the neighborhood of local fault zone takes an important role too, and was responsible for share of implosion in the focal mechanism.     

Pareto Joint Inversion of 2D Magnetotelluric and Gravity Data — Towards Practical Applications

In this paper, a Pareto inversion based global optimization approach, to obtain results of joint inversion of two types of geophysical data sets, is formulated. 2D magnetotelluric and gravity data were used for tests, but presented solution is flexible enough to be used for combination of any kind of two or more target functions, as long as misfits can be calculated and forward problems solved. To minimize dimensionality of the solution, space and introduce straightforward regularization Sharp Boundary Interface (SBI) method was applied. As a main optimization engine, Particle Swarm Optimization (PSO) was used. Synthetic examples based on a real geological model were used to test proposed approach and show its usefulness in practical applications.     

Prospects for Scrutiny of Pulsars with Polish Part of LOFAR

LOFAR (LOw Frequency ARray) is a new generation digitally controlled radio telescope consisting of phased array antenna stations with sensitivity, bandwidth, range of frequency, and digital processing power that makes it an excellent tool for observations of pulsars. This interferometric instrument is able to work in a single-station mode as well as in group-of-selected-stations mode. This article discusses the great opportunity for conducting unique and independent research of pulsar sources with the three LOFAR stations located in Poland and maintained by the POLFAR consortium.     

Natural Radioactivity at the Sin Quyen Iron-Oxide-Copper-Gold Deposit in North Vietnam

The field radiometric and laboratory measurements were performed at the Sin Quyen copper deposit in North Vietnam. The field gamma-ray spectrometry indicated the concentration of uranium ranging from 5.5 to 87 ppm, thorium from 5.6 to 33.2 ppm, and potassium from 0.3 to 4.7%. The measured dose rates ranged from 115 to 582 nGy/h, the highest doses being at the copper ore. Concentrations in the solid samples were in the range of 20–1700 Bq/kg for uranium, 20–92.7 Bq/kg for thorium, and 7–1345 Bq/kg for potassium. The calculated doses were from 22 to 896 nGy/h; both measured and calculated dose rates are mostly related to uranium. Concentrations of radium in water samples were below 0.17 Bq/L. Uranium in water samples was significantly higher than the hydrogeological background; the maximum of 13 Bq/L was at the waste zone pool, but neither radium nor uranium were present in tap water. Radon concentration in the dwelling air was from 42 to 278 Bq/m³ for ²²²Rn and from 8 to 193 Bq/m³ for ²²⁰Rn. The estimated committed dose rates were principally related to ²²²Rn concentration and ranged from 1.1 to 8.1 mSv/y.     

A Variscan continental collision of the West Sudetes and the Brunovistulian terrane: a contribution from structural and metamorphic record of the Stronie Formation,the Orlica-Śnieżnik Dome,SW Poland

Structural, petrological and geochronological data from marbles and mica schists combined with those from highly disputable gneisses and eclogites of the Orlica-Śnieżnik Dome (OSD), gave new insights into Variscan evolution of eastern borderland of the West Sudetes. It is shown that the Variscan tectonometamorphic evolution of the OSD began with E–W oriented subhorizontal shortening (D1 stage) related to the collision of the West Sudetes terranes and the Brunovistulian terrane. The shortening led to generally upright folding, which resulted in formation of the steep N–S trending metamorphic planar fabric S1, thickening of the lithosphere and burial of the Stronie Formation under greenschist facies conditions. As a consequence of subsequent, near-coaxial gravity-controlled vertical shortening (D2), the S1 foliation was deformed in tight recumbent folds F2. The flattening strain was associated with the progression to amphibolite-facies conditions (from ca. 510 upto ca. 620°C) and uplift from depths corresponding to 9–10 kbar to depths corresponding to 7–8 kbar. On microscale, the flattening strain is documented by rotation of the mineral fabric overgrown by syn-D2 prograde garnet porphyroblasts. The Sm–Nd Grt–WR isochron age, correlated with the D2 event yields 346.5 ± 4.4 Ma. Further deformation and progressive metamorphism led to development of the subhorizontally disposed S2 axial plane schistosity, which terminated at the metamorphic temperature peak. During retrogression but still under ductile conditions of deformation, the S2 planes were reactivated during successive top-to-the-N shear movement of the OSD (D3 stage). Due to the mutual interaction of the OSD with the adjacent terranes the shear deformations were localized within marginal parts of these units. Finally, as a result of the NE–SW and the NW–SE oriented shortenings (D4 stage and D5 stage, respectively), both the structural surfaces and metamorphic isograds were regionally folded with W(NW)-ward plunges. A synthesis of new and existing data shows an overall similarity in sequence of Variscan deformations (D1–D2–D3) in the West Sudetes borderland to that observed in the eastern flank of the Moldanubian domain.     

Application of first-arrival tomography to characterize a quick clay landslide site in Southwest Sweden

First-arrival traveltime tomography was applied to high-resolution seismic data acquired over a known quick-clay landslide scar near the Göta River in southwest Sweden in order to reveal the geometry and physical properties of clay-related normally consolidated sediments. Investigated area proved to be a challenging environment for tomographic imaging because of large P-wave velocity variations, ranging from 500 to 6000 m/s, and relatively steeply-dipping bedrock. Despite these challenges, P-wave velocity models were obtained down to ca. 150 m for two key 2D seismic profiles (each about 500-m long) intersecting over the landslide scar. The models portrait the sandwich-like structure of marine clays and coarse-grained consolidated sediments, but the estimated resolution (20 m) is too small to distinguish thin layers within this structure. Modelled velocity structures match well the results of reflection seismic processing and resistivity tomography available along the same profiles.     

Models of the Earth’s crust from controlled-source seismology — Where we stand and where we go?

Controlled-source seismology (CSS) is the primary source of information regarding the fine structure of the lithosphere. The aim of this paper is to provide an overview of the methods that are commonly used to derive Earth models from CSS data with the focus on the wide-angle reflection/refraction method. Some outlook on the future of the CSS is presented with the special emphasis on the full-wavefield based methods like full-waveform inversion, which brings high level of objectivity into modeling, as well as significantly increases spatial resolution. It is stressed that the researchers should be aware of the limitations of how the elastic parameters transcribe into the actual rock properties which should stimulate them to go beyond the simple P-wave modeling and to build multiparameter Earth models based either on the seismic data or constrained by additional geophysical fields in order to derive sound geological interpretation of their models.     

Tectono‐sedimentary evolution of the western Corinth rift (Central Greece)

The Corinth rift (Greece) is one of the world's most active rifts. The early Plio‐Pleistocene rift is preserved in the northern Peloponnese peninsula, south of the active Corinth rift. Although chronostratigraphic resolution is limited, new structural, stratigraphic and sedimentological data for an area >400 km² record early rift evolution in three phases separated by distinct episodes of extension rate acceleration and northward fault migration associated with major erosion. Minimum total N–S extension is estimated at 6.4–7.7 km. The earliest asymmetrical, broad rift accommodated slow extension (0.6–1 mm a^?1) over >3 Myrs and closed to the west. North‐dipping faults with throws of 1000–2200 m defined narrow blocks (4–7 km) with little footwall relief. A N‐NE flowing antecedent river system infilled significant inherited relief (Lower group). In the earliest Pleistocene, significant fluvial incision coincided with a 15 km northward rift margin migration. Extension rates increased to 2–2.5 mm a^?1. The antecedent rivers then built giant Gilbert‐type fan deltas (Middle group) north into a deepening lacustrine/marine basin. N‐dipping, basin margin faults accommodated throws <1500 m. Delta architecture records initiation, growth and death of this fault system over ca. 800 ka. In the Middle Pleistocene, the rift margin again migrated 5 km north. Extension rate increased to 3.4–4.8 mm a^?1. This transition may correspond to an unconformity in offshore lithostratigraphy. Middle group deltas were uplifted and incised as new hangingwall deltas built into the Gulf (Upper group). A final increase to present‐day extension rates (11–16 mm a^?1) probably occurred in the Holocene. Fault and fault block dimensions did not change significantly with time suggesting control by crustal rheological layering. Extension rate acceleration may be due to strain softening or to regional tectonic factors.     

Sea‐level and ocean‐current control on carbonate‐platform growth,Maldives, Indian Ocean

Multichannel high‐resolution seismic and multibeam data were acquired from the Maldives‐isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform evolution, with a special emphasis on sea‐level changes and changes of the oceanic currents. The stacking pattern of Lower to Middle Miocene depositional sequences, with an evolution of a ramp geometry to a flat‐topped platform, reflects variations of accommodation, which here are proposed to be primarily governed by fluctuations of relative sea level. Easterly currents during this stage of bank growth controlled an asymmetric east‐directed progradation of the bank edge. During the late middle Miocene, this system was replaced by a twofold configuration of bank development. Bank growth continued synchronously with partial bank demise and associated sediment‐drift deposition. This turnover is attributed to the onset and/or intensification of the Indian monsoon and related upwelling and occurrence of currents, locally changing environmental conditions and impinging upon the carbonate system. Mega spill over lobes, shaped by reversing currents, formed as large‐scale prograding complexes, which have previously been interpreted as deposits formed during a forced regression. On a regional scale, a complex carbonate‐platform growth can occur, with a coexistence of bank‐margin progradation and aggradation, as well as partial drowning. It is further shown that a downward shift of clinoforms and offlapping geometries in carbonate platforms are not necessarily indicative for a sea‐level driven forced regression. Findings are expected to be applicable to other examples of Cenozoic platforms in the Indo‐Pacific region.